Accessory presence detection

Abstract

Disclosed is an electronic circuit with a first terminal for connecting an accessory thereto, and with a functionality for detecting the presence of an accessory connected to the first terminal.

What is claimed is: 
     
       1. An electronic circuit, comprising:
 a first terminal for connecting a plurality of accessories thereto; 
 a transmitter or receiver circuit connected to the first terminal; 
 a controlled current source comprising an output coupled to the first terminal and configured to drive a current into the first terminal, the current being dependent on an electrical potential at the first terminal; 
 a current measurement circuit coupled to the controlled current source, and configured to measure a current at the first terminal and to provide a current measurement signal that is representative of the current at the first terminal; and 
 an evaluation circuit receiving the current measurement signal and configured to generate a status signal dependent on the current measurement signal, wherein the status signal indicates whether or not one or more of the plurality of accessories are connected to the electronic circuit. 
 
     
     
       2. The electronic circuit of  claim 1 ,
 wherein the controlled current source is configured to provide a controlled output current at its output, 
 wherein the output current is selected from a current range ranging from a minimum current value to a maximum current value, and 
 wherein the controlled current source is configured to provide the output current such that a voltage at the first terminal is limited to a given maximum voltage value. 
 
     
     
       3. The electronic circuit of  claim 1 , wherein the current measurement circuit comprises:
 a first current mirror having an input current path and having an output current path, wherein the input current path is connected in series with the controlled current source; and 
 an impedance connected in series with the output current path, 
 wherein the evaluation circuit is coupled to the impedance. 
 
     
     
       4. The electronic circuit of  claim 3 , wherein the input current path is connected between the controlled current source and the first terminal. 
     
     
       5. The electronic circuit of  claim 4 , wherein the input current path and the output current path are connected in series with the controlled current source. 
     
     
       6. The electronic circuit of  claim 3 , wherein the input current path is connected between a terminal for supply potential and the controlled current source. 
     
     
       7. The electronic circuit of  claim 1 , wherein the controlled current source comprises:
 a controllable current source having a current output coupled to the output of the controlled current source and a control input; and 
 a feedback loop coupled between the first terminal and the control input. 
 
     
     
       8. The electronic circuit of  claim 7 , wherein the feedback loop comprises an amplifier having a first input coupled to the first terminal, a second input receiving a reference voltage, and an output connected to the control input. 
     
     
       9. The electronic circuit of  claim 1 , wherein the controlled current source comprises:
 a reference current source; and 
 a second current mirror with an input current path connected in series with the reference current source, and an output current path coupled to the output of the controlled current source. 
 
     
     
       10. The electronic circuit of  claim 9 , wherein the controlled current source is coupled to the first terminal only via the output. 
     
     
       11. The electronic circuit of  claim 9 , wherein the second current minor further comprises:
 an input transistor having a control terminal, and having a load path forming the input current path; 
 an output transistor having a control terminal coupled to the control terminal of the input transistor, and having a load path forming the output current path; and 
 a feedback loop coupled between the first terminal and the control terminals of the input and the output transistors. 
 
     
     
       12. The electronic circuit of  claim 3 , wherein the controlled current source comprises:
 a reference current source; and 
 a second current mirror with an input current path connected in series with the reference current source, and an output current path coupled to the output of the controlled current source; 
 wherein the first and second current mirrors have a common input current path. 
 
     
     
       13. The electronic circuit of  claim 12 , wherein the second current minor further comprises:
 an input transistor having a control terminal, and having a load path forming the input current path; 
 an output transistor having a control terminal coupled to the control terminal of the input transistor, and having a load path forming the output current path; and 
 a feedback loop coupled between the first terminal and the control terminals of the input and the output transistors. 
 
     
     
       14. The electronic circuit of  claim 1 , wherein the accessory is a removable component. 
     
     
       15. The electronic circuit of  claim 1 , wherein the plurality of accessories comprise a transmitter and/or receiver circuit configured for data communication via a single line. 
     
     
       16. The electronic circuit of  claim 1 , wherein the plurality of accessories comprise a transmitter and/or receiver circuit configured for data communication, wherein the transmitter and/or receiver circuit is configured to modulate a voltage at the first terminal. 
     
     
       17. The electronic circuit of  claim 1 , wherein the plurality of accessories comprise a transmitter and/or receiver circuit configured for data communication, wherein the transmitter and/or receiver circuit is configured to receive/detect an output voltage at the first terminal. 
     
     
       18. An electronic circuit comprising:
 a first terminal for connecting an accessory thereto; 
 a transmitter or receiver circuit connected to the first terminal; 
 a controlled current source comprising an output coupled to the first terminal and configured to drive a current into the first terminal, the current being dependent on an electrical potential at the first terminal; 
 a current measurement circuit configured to measure a current at the first terminal and to provide a current measurement signal that is representative of the current at the first terminal; and 
 an evaluation circuit receiving the current measurement signal and configured to generate a status signal dependent on the current measurement signal, wherein the evaluation circuit comprises:
 a first comparator stage configured to compare the current measurement signal with a first reference signal and configured to provide a first comparator signal dependent on the comparison result; and 
 an output stage having at least one input for receiving the first comparator signal or a signal dependent on the first comparator signal, and configured to provide the status signal dependent on a signal received at the at least one input. 
 
 
     
     
       19. The electronic circuit of  claim 18 , wherein the evaluation circuit further comprises:
 an enable comparator stage configured to compare the current measurement signal with an enable reference signal and to provide an enable comparator signal; and 
 an enable input of the output stage at which the enable reference signal or a signal dependent on the enable reference signal is received; 
 wherein the output stage is configured to provide the status signal dependent on the signal received at the at least one first input and dependent on the signal received at the enable input. 
 
     
     
       20. The electronic circuit of  claim 18 , wherein the evaluation circuit further comprises:
 a first delay stage connected between the first comparator stage and the output stage and configured to delay at least one of a rising and a falling edge of the first comparator signal. 
 
     
     
       21. The electronic circuit of  claim 18 , further comprising:
 at least one further comparator stage configured to compare the current measurement signal with a further reference signal and to provide a further comparator signal; and 
 a further input of the output stage receiving the further comparator signal or a signal dependent on the further comparator signal; 
 wherein the output stage is configured to also generate the status signal dependent on the signal received at its further input. 
 
     
     
       22. The electronic circuit of  claim 21 , wherein the status signal comprises at least two sub-signals including a first sub-signal that is dependent on the signal received at the first input of the output stage and a further sub-signal that is dependent on the signal received at the further input of the output stage. 
     
     
       23. An electronic circuit, comprising:
 a first terminal for connecting a plurality of removable components thereto; 
 a transmitter or receiver circuit connected to the first terminal; 
 a voltage controller comprising an output coupled to the first terminal and configured to drive a current into the first terminal such that a voltage at the first terminal assumes a reference value, wherein the current is limited to a maximum current; 
 a current measurement circuit coupled to the voltage controller, and configured to measure a current at the first terminal and to provide a current measurement signal that is representative of the current at the first terminal; and 
 an evaluation circuit receiving the current measurement signal and configured to generate a status signal dependent on the current measurement signal, wherein the status signal indicates whether or not one or more of the plurality of removable components are connected to the electronic circuit. 
 
     
     
       24. An electronic circuit comprising:
 a first terminal for connecting an accessory thereto; 
 a transmitter or receiver circuit connected to the first terminal; 
 a voltage controller comprising an output coupled to the first terminal and configured to drive a current into the first terminal such that a voltage at the first terminal assumes a reference value, wherein the current is limited to a maximum current; 
 a current measurement circuit coupled to the voltage controller, and configured to measure a current at the first terminal and to provide a current measurement signal that is representative of the current at the first terminal; and 
 an evaluation circuit receiving the current measurement signal and configured to generate a status signal dependent on the current measurement signal, wherein the evaluation circuit comprises
 a first comparator stage configured to compare the current measurement signal with a first reference signal and configured to provide a first comparator signal dependent on the comparison result, and 
 an output stage having at least one input for receiving the first comparator signal or a signal dependent on the first comparator signal, and configured to provide the status signal dependent on a signal received at the at least one input. 
 
 
     
     
       25. An electronic circuit, comprising:
 a first terminal for connecting an accessory thereto; 
 a transmitter or receiver circuit connected to the first terminal; 
 a controlled current source comprising an output coupled to the first terminal and configured to drive a current into the first terminal, the current being dependent on an electrical potential at the first terminal; 
 a current measurement circuit coupled to the controlled current source, and configured to measure a current at the first terminal and to provide a current measurement signal that is representative of the current at the first terminal; and 
 an evaluation circuit receiving the current measurement signal and configured to generate a status signal dependent on the current measurement signal, wherein the status signal indicates whether or not the accessory is connected to the electronic circuit; and 
 wherein the accessory comprises a transmitter and/or receiver circuit configured for data communication, wherein the transmitter and/or receiver circuit is configured to modulate a voltage at the first terminal and/or receive/detect an output voltage at the first terminal.